Applied a slightly modified version of a patch from

Applied a slightly modified version of a patch from
Neil Spring <nspring@cs.washington.edu> that declares strings as
const where applicable. It also changes our CFLAGS to be much
stricter and removes the warnings introduced by -Wwrite-strings.
This allows building other check tests with -Wwrite-strings
without heaping gobs of compiler warnings.

git-svn-id: svn+ssh://svn.code.sf.net/p/check/code/trunk@127 64e312b2-a51f-0410-8e61-82d0ca0eb02a